A jar contains $11$ red balls, $8$ green balls, and $10$ blue balls. If a ball is randomly chosen, what is the probability that it is not green?
There are $11 + 8 + 10 = 29$ balls in the jar. There are $8$ green balls. That means $29 - 8 = 21$ are not green. The probability is $ \frac{21}{29}$.